Rheostat.



No. 7l3,60|. Pa'tonted Nov. I8, 8902.

F. E. CASE.

. RHEOSTAT.

(Apphcltion filed may 10, 1901. (.No Model.) 2 Shouts-Sheet I.

WIDTICSSG? I Inventor.

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No. 7l3,60|. Patented Nov. l8, I902.

r. E. CASE.

BHEOSTAT.

(Applica-tion filed Kay 10, 1901.

(I0 Iddel.) 2 Sheets-Sheot 2.

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UNITED STATES PATENT OFFICE.

FRANK E. CASE, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NElV YORK.

RHEOSTAT.

SPECIFICATION forming part of Letters Patent No. 713,601, dated November 18, 1902.

Application filed May 10,1901. Serial No. 59,590. (No model.)

To all whom it may concern."

Be it known that I, FRANK E. CASE, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New 5 York, have invented certain new and useful Improvementsiu Rheostats, (Case No. 1,777,) of which the following is a specification.

This invention relates to improvements upon the generic type of resistance device IO shown in the patent to Short, No. 159,79-t, September 22, 1891.

The invention consists in the construction and arrangement whereby the rheostat is made light, adapted to be readily cooled, and

I5 to be mounted in a simple manner on the lower side of the floor of a railway-car.

This rheostat is especially adapted for use on electric cars or trains, where it is cut in and out of the motor-circuit by the controller,

in order to vary the speed and torque of the car-motors. The rheostat described herein is one of the several units which are usually employed in connection with the motors on each car. The chief advantages over the Short patent noted above are the greatly-reduced weight and the greatly-increased heatradiating surface which is exposed to the air. In fact, the rheostat has an effective resistance portion which comprises at least sixty per cent. of the entire weight, and substantially all of this resistance is freely exposed to the circulation of air-currents. At the date of the Short patent it was considered essential that the grids which make up the rheostat should be separated from each other by insulatiug-strips. This left only the edges of the grids freely exposed to the air, and in order to provide for cooling the grids auxiliary heat-conducting plates were interposed at intervals throughout the rheostat. Thus the structure was not only greatly increased in weight, but all the opposing faces of the grids were covered up by insulation, and the spaces between adjacent grids were filled up with this insulation, so that the only surfaces exposed for radiation were the outside edges of the grids and the edges of the perforations formed through the grids, the insulatingstrips, and the auxiliary heatconducting plates. In accordance with my invention a structure is provided which is adapted to be readily attached to the bottom of a car, and all insulation between the main portions of the grids and all auxiliary heat-conducting plates are dispensed with, the grids being so mounted that the main portion of each grid is separated by air-spaces from the main portions of adjacent grids. Thus substantially theentire surfaces of all the grids are exposed to the air, so that the resistance can quickly cool, and the weight is reduced to nearly one-half of that of rheostats of this type which have hitherto been used.

Of the drawings, Figure 1 is a perspective View of arheostat constructed in accordance with the invention. Fig. 2 is a cross-section of the same, showing a single grid and an end plate in elevation; and Fig. 3 is a plan of the structure.

' As shown in Figs. 1 and 2, each grid G comprises a conductor, which extends in a zigzag manner, so that many hundreds of feet of resistance are contained in a single unit, such as that shown in Fig. 1. Each grid is formed with hubs H, which are perforated, so that they can be slid over the supporting-rods R. These rods R are firstprovided with an insulating-sheath S, of mica or other suitable insulating material, and after the sheath is in place the grids are slipped over them. Each grid is also formed with two perforated bosses F, adapted to receive circuit-terminals L, so that any number of grids can be connected or inserted permanently in circuit, as desired. The grids are preferably composed of castiron, the hubs H and bosses F being cast integral. However, any other desired construction which is substantially the same and by which the same results are obtained is considered to be within the scope of the invention. The grids are mounted upon the insulating and supporting rods R in the manner shown in Fig. 3. The two outside rods R serve as the main supports for the grids; but in order that grids of considerable width can 5 be employed a third insulating and supporting rod R is provided and is covered with insulation. Each grid is formed with an additional hub H for fitting this third rod. The grids are made thicker at the hubs, so as to ICC hold them spaced apart and also provide sufficient bearing-surface at the points of engagement with the insulated supporting-rods to withstand the wrenching effect due to the inertia of the individual grids and the length of the arm between their centers of gravity and supports. In order to strengthen the grids, so that they may not break under these wrenching strains, the sections to which the hubs are attached are gradually increased in thickness, as shown in Fig. 1, up to the thickness of the hubs. As shown in Fig. 2, the outside hubs are ofiset so'as to permit the intermediate loops of the grid to extend to the level of the upper side of the hubs. The middle hub is not ofiset, and in order that the loops on either side thereof may not crowd it they are made shorter. By this arrangement of hubs relatively to the loops the vertical length of the grids is not shortened to accommodate the supporting rods. Beginning with the left-hand grid in Fig. 3 this grid is slipped on the rods from the right, and then over the upper rod is slipped an insulating-disk G, of mica. A similar insulatingdisk 0, of mica, is slipped over the middle rod R. Then a second grid is slipped over all three rods, so that its lower hub engages and makes contact with the lower hub of the first grid, but its other two hubs are insulated from the other two hubs of the first grid by the insulating-disks O and 0'. Next two insulating-disks are slipped over the middle and lower rods, and a third grid is slipped over all three rods, so that its upper hub is in engagement and makes contact with the upper hub of the second grid, its other two hubs being insulated from the other hubs of the second grid by the insulating-disks. It will thus be seen that these three grids are in series and that the hubs serve to separate the grids from each other by air-spaces, 'so that the entire surfaces of the grids, with the exception of the surfaces between adjacent hubs and the inside of the hubs which rest on the rods, are exposed to the air. The remainder of the rheostat is constructed as described with respect to the first three grids, and the leads L are inserted on the perforated bosses F of the two end grids, the leads being held in said bosses by the binding-screws A. It will be observed that the portions of the bosses F which join each other are cut away, as shown at U, so that the creepagesurface adjacent to the insulating-disk O is very much increased. This construction obviates the necessity of the use of disks of larger diameter and effects the same result. The means for clamping the grids on the rods, for attaching the structure to the bottom of the car, and for protecting the grids against injury comprises the metal end plates P, which are provided with perforations for the ends of the rods and also with shoulders D,

formed with oblong slots 0 for the reception.

of bolts for attachment to the bottom of the car. As seen in Figs. land 2, these end plates are formed with large perforations E, which expose a large portion of the sides of the end grids to the air, so that only a very small portion of the end grids are covered by the plates. Thus the entire structure is open from end to end through the end plates. The slots 0 of the shoulders D are made oblong, so that in case the grids become worn or loose the plates may be clamped up to retain the hubs in contact, which is necessaryin order that the circuit may be maintained closed. The shoulders are preferably so located on the bottom of a car that the end plates will lie parallel to the direction of motion of the car, so that the portion of the structure between the end plates will be face to face with the rush of air due to the motion of the car. For automatically maintaining the circuit closed pending the readjustment of the end plates there are provided metal spring-washers K, which are interposed, preferably, between the hubs of the grids and the end plates, and these spring-washers automatically take up the play of the parts and maintain the hubs in contact. Moreover, the grids are by the action of washers K, in addition to the long bearing of the hubs upon the insulated supporting-rods, securely held at right angles to the rods. Disks M, which are preferably composed of a suitable insulating compound, are located adjacent to the end hubs, and metal washers J and J are interposed between the insulating-disks and the spring-washers.

As shown in Figs. 1 an 2, not only are the end plates suspended from the car-bottom, but also the grids themselves are suspended from the insulating and supporting rods, all of which arein alinement with the tops of the end plates. Thus the grids hang vertically down ward, and their inherent rigidity is relied upon to prevent them from coming in contact with each other. The lower ends of the end plates are preferably maintained rigidly in position by rods or bolts B.

As shown in Fig. 3, the end plates'have bosses Q and Q formed integral on their outside faces at the portions where the plates are perforated for the reception of the supporting-rods. The ends of the rods which extend beyond the plates are not insulated, but are threaded for the reception of nuts N and N.

Hence insulating-rings I and I are placed adscribed. For example, it is obvious that the hubs might be in the form of hooks, as it is not essential that they be complete circles. An additional purpose of the hubs is to form air-spaces between the grids. However, any other means for accomplishing this result in substantially the same manner is an equivaarated by air-spaces from adjacent grids, and

end plates covering and protecting the end grids and adapted to bear upon only the hubs of said end grids for clamping the grids on the rods, said plates being constructed and arranged to be secured to the bottom of a car and perforated to permit free access of air to the grids.

2. In a rheostat for railway-cars, the combination with insulating and supporting rods, of a plurality of resistance-grids, each pro vided with perforated hubs'by which it is mounted on the rods so that its greater portion is separated by air-spaces from adjacent grids, end plates for clamping the grids on the rods, shoulders on the end plates, and oblong slots in the shoulders, whereby the structure can be so suspended from the bottom of a car that the plates can be adjusted to always tightly clamp the grids on the rods.

3. In a rheostat for railway-cars, the combination with insulating supporting-rods, of a plurality of resistance-grids, each provided with perforated hubs by which its greater portion is separated by air-spaces from adjacent grids, end plates for clamping the grids on the rods, nuts on the ends of the rods outside the end plates, insulating-washersinterposed between the plates and the nuts, and bosses on the outside of the end plates and of smaller diameter than the washers, whereby the surface insulation is increased.

at. In a rheostat for railway-cars, the combination with insulating supportingrods, of a plurality of resistance-grids, each provided with perforated hubs by which it is mounted on the rods so that its greater portion is separated by air-spaces from adjacent grids, end plates for clamping the grids on the rods, which bear upon only the hubs of the outer grids, nuts on the ends of the rods outside of the end plates, and insulating-washers interposed between the plates and the nuts.

5. In a rheostat for railway-cars, the combination with insulating supporting-rods, of a plurality of resistance-grids, each provided with perforated hubs by which it is mounted on the rods so that its greaterportion is separated by air-spaces from adjacent grids, insulating-disks on the rods on opposite sides of adjacent pairs of hubs, metal end plates for clamping the hubs together to connect the grids in series, a spring-washer suitably interposed to maintain the electrical connection of the hubs, and an insulating-washer mounted on the rods to insulate the hubs from the end plates.

6. In a rheostat for railway-cars, the combination with insulating supporting-rods, of a plurality of resistance-grids, each provided with perforated hubs by which it is mounted on the rods so that its greater portion is separated by air-spaces from adjacent grids, insulating-disks on the rods on opposite sides of adjacent pairs of hubs, end plates for clamping the hubs together so that the grids are connected in series, and a spring-washer suitably interposed to maintain the electrical connection of the hubs.

7. In a rheostat for railway-cars, the combination with insulating supporting-rods, of a plurality of resistance-grids, each provided with hubs by which itis mounted 011 the rods so that its greater portion is separated by airspaces from adjacent grids, insulating-disks on the rods between the hubs and terminal bosses formed in the hubs and cut away adjacent to the insulating-disks toincrease the creepage-surface.

8. In arheostat, the combination with three insulating supporting-rods, of a plurality of resistance-grids, each provided at its upper portion with three perforated hubs, whereby the grid is suspended from the rods, so that its greater portion is separated by air-spaces from the grids on either side, insulating-disks on the outside rods on opposite sides of each adjacent pair of hubs, insulating-disks on the intermediate rod on opposite sides of each hub, and means for clamping the hubs together, whereby all the grids are connected in series.

9. In a rheostat, the combination with three insulating supporting-rods, of a plurality of resistance-grids, each provided with three perforated hubs, whereby the grid is mounted on the three rods, so that its greater portion is separated from adjacent grids by airspaces, insulating-disks on the outside rods on opposite sides of each adjacent pair of hubs, insulating-disks on the intermediate rod on opposite sides of each hub, and means for clamping the hubs together, whereby all the grids are connected in series.

10. In a rheostat for railway-cars, the eo1nbination with insulating supporting-rods, of a plurality of resistance-grids provided at their upper portions with perforated hubs by which they are suspended from the rods so that all the remaining portions of the grids are separated from each other by air-spaces, and end plates for clamping the grids on the rods, which bear upon the end grids only at the hubs thereof, said plates extending above the tops of the grids, where they are provided with means for suspending the structure from the bottom of the car.

11. In a rheostat for railway-cars, the combination with insulating supporting-rods, of a plurality of resistance-grids provided at their upper ends with perforated hubs by which they are suspended from the rods so that all the remaining portions of the grids are separated from each other by air spaces, end

plates for clamping the grids on the rods, which bear upon only the hubs of the end grids, said plates extending from top to bottom of the grids to protect the same, and also extending below the grids, and rods independent of the grids for holding the lower portions of the plates together.

12. In a rheostat for railway-cars, the combination with insulating supporting-rods, of a plurality of resistance-grids provided at .their upper ends with perforated hubs by which they are suspended on the rods so that all the remaining portions of the grids are separated from each other by air-spaces, and end plates for clamping the grids on the rods and suspending the structure from the bottom of a car, the said plates being adapted to protect the whole of the end grids, and at the same time bear upon only the hubs of said end grids.

13. In a rheostat for railway-cars, the combination with insulating supporting-rods, of a plurality of resistance-grids formed with perforated hubs by which they are mounted on the rods so that the grids are separated by airspaces, disks on the rods which separate the hubs from each other, and end plates for clamping the grids on the rods, and provided with means for suspension from the bottom of a car, the said plates being adapted to protect the whole of the end grids, and at the same time bear upon only the hubs of said end grids.

14. In a rheostat for railway-cars, the combination with insulating supporting-rods, of a pluralityof resistance-grids separated by airspaces and carried by said rods, disks around the rods for insulating adjacent portions of the grids from each other,end plates for clamping the grids in position on the rods, and shoulders on the end plates whereby the structure can be suspended from the bottom of a car; the.

said plates being adapted to protect the whole of the end grids, and at the same time bear upon only the hubs of said end grids.

15. A grid for rheostats consisting of a series of coils or loops of resistance'material, some of of reversely-disposed coils or loops of resistance material which terminate in offset hubs.

17. A grid for rheostats comprising a series of reversely-disposed coils or loops of resistance material, the ends of which terminate in oflsetsupporting-hubs and the middle coils or loops of which are made short and one of said middle coils or loops provided with a supporting-hub.

18. In a rheostat, the combination of an insulating bar or bars and a plurality of resistance-grids provided near one end with thickened hubs adapted to engage said bar or bars and be supported wholly thereby.

In witness whereof I have hereunto set my hand this 8th day of May, 1901.

FRANK E. CASE.

Witnesses:

BENJAMIN B. HULL,

FRED Ross. 

